System and method for determining vessel size and/or edge

ABSTRACT

A surgical system used to determine a size of a vessel within a region proximate to a working end of a surgical instrument includes at least one light emitter disposed at the working end, an array of light sensors disposed opposite the at least one light emitter, the array comprising a least one row of light sensors, individual light sensors in the row adapted to generate a signal comprising a pulsatile and a non-pulsatile component, and a controller coupled to the array, the controller comprising a splitter to separate the pulsatile component from the non-pulsatile component, and an analyzer to determine the magnitudes of the pulsatile and non-pulsatile components at the individual light sensors, to determine a first peak magnitude and a second peak magnitude of the pulsatile components, and to determine a resting outer diameter of the vessel based on the first and second peak magnitudes.

The present application is a U.S. National Stage of PCT InternationalPatent Application No. PCT/US2016/018805, filed on Feb. 19, 2016, whichclaims priority to Provisional Patent Application No. 62/118,443, filedFeb. 19, 2015, and Provisional Patent Application No. 62/118,554, filedFeb. 20, 2015, all three of which are hereby incorporated herein byreference.

BACKGROUND

This patent is directed to a system and method for determining the sizeand/or the edge of a vessel, such as a blood vessel, and in particularto a system and method using the light transmitted to a sensor arraythat includes a pulsating component.

Systems and methods that identify artifacts, and in particular vessels,in the surgical field during a surgical procedure provide valuableinformation to the surgeon or surgical team. U.S. hospitals losebillions of dollars annually in unreimbursable costs because ofinadvertent vascular damage during surgery. In addition, the involvedpatients face a mortality rate of up to 32%, and likely will requirecorrective procedures and remain in the hospital for an additional ninedays, resulting in tens, if not hundreds, of thousands of dollars inadded costs of care. Consequently, there is this significant value to beobtained from methods and systems that permit accurate determination ofthe presence of vessels, such as blood vessels, in the surgical field,such that these costs may be reduced or avoided.

Systems and methods that provide information regarding the presence ofblood vessels in the surgical field are particularly important duringminimally-invasive surgical procedures. Traditionally, surgeons haverelied upon tactile sensation during surgical procedures both toidentify blood vessels and to avoid inadvertent damage to these vessels.Because of the shift towards minimally-invasive procedures, includinglaparoscopic and robotic surgeries, surgeons have lost the ability touse direct visualization and the sense of touch to make determinationsas to the presence of blood vessels in the surgical field. Consequently,surgeons must make the determination whether blood vessels are presentin the surgical field based primarily on convention and experience.Unfortunately, anatomical irregularities frequently occur because ofcongenital anomalies, scarring from prior surgeries, and body habitus(e.g., obesity).

While the ability to determine the presence or absence of a vesselwithin the surgical field provides valuable advantages to the surgeon orsurgical team and is of particular importance for minimally-invasiveprocedures where direct visualization and tactile methods ofidentification have been lost, the ability to characterize theidentified vasculature provides additional important advantages. Forexample, it would be advantageous to provide information relating to thesize of the vessel, such as the inner or outer diameter of the vessel.As another example, it would be advantageous to provide informationrelating to the edges of the vessel. Size information and/or edgedetection is particularly relevant as the Food and Drug Administrationpresently approves, for example, thermal ligature devices to seal andcut vessels within a given size range, typically less than 7 mm indiameter for most thermal ligature devices. If a thermal ligature deviceis used to seal a larger blood vessel or only part of a vessel, then thefailure rate for a seal thus formed may be as high as 19%.

In addition, it would be preferable to provide this information withminimal delay between vessel detection and vessel analysis, such thatthe information may be characterized as real-time. If considerable timeis required for analysis, then at a minimum this delay will increase thetime required to perform the procedure. In addition, the delay mayincrease surgeon fatigue, because the surgeon will be required to moveat a deliberate pace to compensate for the delay between motion of theinstrument and delivery of the information. Such delays may in facthinder adoption of the system, even if the information provided reducesthe risk of vascular injury.

Further, it would be advantageous to detect and analyze the vasculaturewithout the need to use a contrast medium or agent. While the use of acontrast agent to identify vasculature has become conventional, the useof the agent still adds to the complexity of the procedure. The use ofthe agent may require additional equipment that would not otherwise berequired, and increase the medical waste generated by the procedure.Further, the use of the contrast agent adds a risk of adverse reactionby the patient.

As set forth in more detail below, the present disclosure describes asurgical system including a system and method for determining vesselsize and/or detecting the edges of a vessel embodying advantageousalternatives to the existing methods, which may provide for improvedidentification for avoidance or isolation of the vessel.

SUMMARY

According to an aspect of the present disclosure, a surgical system usedto determine a size of a vessel within a region proximate to a workingend of a surgical instrument includes at least one light emitterdisposed at the working end of the surgical instrument, and an array oflight sensors disposed at the working end of the surgical instrumentopposite the at least one light emitter, the array of light sensorscomprising a least one row of light sensors, individual light sensors inthe row of light sensors adapted to generate a signal comprising a firstpulsatile component and a second non-pulsatile component. The systemalso includes a controller coupled to the array of light sensors, thecontroller comprising a splitter to separate the first pulsatilecomponent from the second non-pulsatile component and an analyzer todetermine the magnitudes of the pulsatile and non-pulsatile componentsat the individual light sensors in the row of light sensors, todetermine a first peak magnitude and a second peak magnitude of thepulsatile components, to determine a resting outer diameter of thevessel based on the first and second peak magnitudes of the pulsatilecomponents.

According to another aspect of the present disclosure, a method ofdetermining a size of a vessel within a region proximate to a workingend of a surgical instrument includes emitting light at the working endof the surgical instrument, sensing light at the working end of thesurgical instrument at an array of light sensors comprising at least onerow of light sensors, separating a first pulsatile component from asecond non-pulsatile component for individual sensors along the row oflight sensors, determining the magnitudes of the pulsatile andnon-pulsatile components at the individual light sensors in the row oflight sensors, determining a first peak magnitude and a second peakmagnitude of the pulsatile components, and determining a resting outerdiameter of the vessel based on the first and second peak magnitudes ofthe pulsatile components.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure will be more fully understood from the followingdescription taken in conjunction with the accompanying drawings. Some ofthe figures may have been simplified by the omission of selectedelements for the purpose of more clearly showing other elements. Suchomissions of elements in some figures are not necessarily indicative ofthe presence or absence of particular elements in any of the exemplaryembodiments, except as may be explicitly delineated in the correspondingwritten description. None of the drawings is necessarily to scale.

FIG. 1 is a schematic diagram of a surgical system according to anembodiment of the present disclosure;

FIG. 2 is an enlarged, fragmentary view of the surgical instrument withlight emitter and light sensors according to FIG. 1 with a section of avessel illustrated as disposed between the light emitter and lightsensors;

FIG. 3 is an enlarged cross-sectional view of a blood vessel with thewall expanding and contracting as blood flows through the vessel, withthe change in outer diameter between a resting state and an expandedstate exaggerated to better illustrate the changes in blood vessel outerdiameter;

FIG. 4 is a flow diagram of a method according to an embodiment of thepresent disclosure, which method may be carried out using the system ofFIG. 1;

FIG. 5 is a flow diagram of particular actions that may be performed aspart of the method illustrated in FIG. 4;

FIG. 6 is a graph of the magnitudes of the pulsatile (AC) andnon-pulsatile (DC) components for each of the elements (pixels) of alight sensor array, the graph being used to illustrate general conceptsdisclosed herein;

FIG. 7 is a flow diagram of alternate actions that may be performed aspart of the method illustrated in FIG. 4;

FIG. 8 is a graph comparing the outer diameters of various porcinearteries relative to the inner diameters of these arteries;

FIG. 9 is a flow diagram of a method according to an alternateembodiment of the present disclosure, which method may be carried outusing the system of FIG. 1;

FIG. 10 is a flow diagram of a method according to a further alternateembodiment of the present disclosure, which method may be carried outusing the system of FIG. 1;

FIG. 11 is a simulated partial screen capture of a video monitor used inthe system of FIG. 1;

FIG. 12 is a graph of the magnitudes of the pulsatile (AC) andnon-pulsatile (DC) components for each of the elements (pixels) of alight sensor array (linear CCD array) used in a first set ofexperiments;

FIG. 13 is a graph of the magnitudes of the pulsatile (AC) andnon-pulsatile (DC) components for each of the elements of a light sensorarray (photodetector array, with measurements presented in pixels forcomparison with FIG. 7) used in a second set of experiments;

FIG. 14 is a graph comparing the inner diameters of various porcinearteries as determined using a light sensor array (linear CCD array) andas measured in a third set of experiments;

FIGS. 15 and 16 relate to a first experiment performed using systems andmethods of edge detection according to an embodiment of the presentdisclosure;

FIGS. 17 and 18 relate to a second experiment performed using systemsand methods of edge detection according to an embodiment of the presentdisclosure;

FIGS. 19 and 20 relate to a third experiment performed using systems andmethods of edge detection according to an embodiment of the presentdisclosure; and

FIGS. 21 and 22 relate to a fourth experiment performed using systemsand methods of edge detection according to an embodiment of the presentdisclosure

DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS

A surgical system according to an embodiment of the present disclosureincludes at least one light emitter, at least one light sensor, and acontroller. The system may also include a surgical instrument as well.

The system determines a size and/or an edge or edges of a vessel withina region proximate to a working end of the surgical instrument. Inparticular, it is believed that the system may be used to determine thesize and/or edges of a vessel within the region proximate to the workingend of the surgical instrument regardless of the presence or the type oftissue surrounding the vessel. The embodiments of the system describedbelow perform determinations relative to the presence and size of thevessel within the targeted region based on the light transmittance asdetermined by the light sensor, and thus the embodiments may appearfacially similar to the technology used in transmissive pulse oximetryto determine the oxygen saturation (i.e., the percentage of bloodhemoglobin that is loaded with oxygen). Careful consideration of thefollowing disclosure will reveal that the disclosed system utilizes thelight emitter(s) and light sensor(s) in conjunction with a controller(either in the form of unique circuitry or a uniquely programmedprocessor) to provide information regarding the presence and size ofvessels that would not be provided by a pulse oximeter. Further, thedisclosed embodiments include the use of a sensor array, the controllerprocessing the pulsatile and non-pulsatile components of signals fromthat array to yield information regarding the diameter(s) of the vessel(e.g. the inner diameter or the resting outer diameter). Moreover, thedisclosed technology may be utilized with vessels other than bloodvessels, further separating the disclosed system and method from atransmissive pulse oximeter.

FIGS. 1 and 2 illustrate an embodiment of such a surgical system 100used to determine a size (e.g., diameter) and/or an edge or edges of avessel, V, within a region 102 of tissue, T, proximate to a working end104 of a surgical instrument 106. It will be understood that the vesselV may be connected to other vessels with the region 102 of tissue T, andin addition, the vessel V may extend beyond the region 102 so as to bein fluid communication with other organs (e.g., the heart) also found inthe body of the patient. Furthermore, while the tissue T appears inFIGS. 1 and 2 to surround fully the vessel V (in terms of bothcircumference and length) to a particular depth, this need not be thecase in all instances where the system 100 is used. For example, thetissue T may only partially surround the circumference of and/or onlysurround a section of the length of the vessel V, or the tissue T mayoverlie the vessel V in a very thin layer. As further non-limitingexamples, the vessel V may be a blood vessel, and the tissue T may beconnective tissue, adipose tissue or liver tissue.

The surgical system 100 includes at least one light emitter 110 (orsimply the light emitter 110), at least one light sensor or detector 112(or simply the light sensor 112), and a controller 114 coupled to thelight emitter 110 and the light sensor 112. As noted above, the system100 also may include the surgical instrument 106.

The light emitter 110 is disposed at the working end 104 of the surgicalinstrument 106. The light sensor 112 is also disposed at the working end104 of the surgical instrument 106. As illustrated in FIGS. 1 and 2, thelight sensor 112 may be disposed opposite the light emitter 110 becausethe light emitter 110 and the light sensor 112 are disposed on opposingelements of the surgical instrument 106, as explained in detail below.

The light emitter 110 is adapted to emit light of at least onewavelength. For example, the light emitter 110 may emit light having awavelength of 660 nm. This may be achieved with a single element, or aplurality of elements (which elements may be arranged or configured intoan array, for example, as explained in detail below). In a similarfashion, the light sensor 112 is adapted to detect light at the at leastone wavelength (e.g., 660 nm). According to the embodiments describedherein, the light sensor 112 includes a plurality of elements, whichelements are arranged or configured into an array.

According to certain embodiments, the light emitter 110 may beconfigured to emit light of at least two different wavelengths, and thelight sensor 112 may be configured to detect light at the at least twodifferent wavelengths. For example, the light emitter 110 may emit lightof three wavelengths, while the light sensor may detect light of threewavelengths. As one example, the light emitter 110 may emit and thelight sensor 112 may detect light in the visible range, light in thenear-infrared range, and light in the infrared range. Specifically, thelight emitter 110 may emit and the light sensor 112 may detect light at660 nm, at 810 nm, and at 940 nm. Such an embodiment may be used, forexample, to ensure optimal penetration of blood vessel V and thesurrounding tissue T under in vivo conditions.

In particular, the light emitted at 810 nm may be used as a reference toremove any variations in the light output because of motion and/or bloodperfusion. The 810 nm wavelength corresponds to the isobestic point,where the absorption for both oxygenated and deoxygenated hemoglobin isequal. Consequently, the absorption at this wavelength is independent ofblood oxygenation and is only affected by the change in lighttransmittance because of motion and/or changes in perfusion.

As stated above, the light sensor may be in the form of an array oflight sensors. In fact, the array of light sensors 112 further includesat least one row of light sensors (see FIG. 2); according to certainembodiments, the array 112 may include only a single row of lightsensors, and the array 112 may be referred to in the alternative as alinear array. The at least one row of light sensors 112 includes aplurality of individual light sensors. The individual light sensors 112may be disposed adjacent each other, or the light sensors may be spacedfrom each other. It may even be possible for the individual lightsensors that define a row of light sensors to be separated from eachother by light sensors that define a different row or column of thearray. According to a particular embodiment, however, the array maycomprise a charge coupled device (CCD), and in particular linear CCDimaging device comprising a plurality of pixels.

According to the embodiments of this disclosure, the individual lightsensors 112 (e.g., pixels) are adapted to generate a signal comprising afirst pulsatile component and a second non-pulsatile component. It willbe recognized that the first pulsatile component may be an alternatingcurrent (AC) component of the signal, while the second non-pulsatilecomponent may be a direct current (DC) component. Where the light sensor112 is in the form of an array, such as a CCD array, the pulsatile andnon-pulsatile information may be generated for each element of thearray, or at least for each element of the array that defines the atleast one row of the array.

As to the pulsatile component, it will be recognized that a blood vesselmay be described as having a characteristic pulsation of approximately60 pulses (or beats) per minute. While this may vary with the patient'sage and condition, the range of pulsation is typically between 60 and100 pulses (or beats) per minute. The light sensor 112 will produce asignal (that is passed to the controller 114) with a particular ACwaveform that corresponds to the movement of the blood through thevessel. In particular, the AC waveform corresponds to the lightabsorption by the pulsatile blood flow within the vessel. On the otherhand, the DC component corresponds principally to light absorption andscattering by the surrounding tissues.

In particular, it is believed that the elements of the light sensorarray 112 disposed on the opposite side of the vessel V from the lightemitter 110 will have a higher AC signal than those elements where thevessel V is not disposed between the light emitter 110 and the lightsensor array 112, because the most marked fluctuations in thetransmitted light will be caused by the vessel-associated pulsations. Itis also believed that the elements of the array 112 disposed on theopposite side of the vessel V from the light emitter 110 will have adecreased DC signal compared to elements of the array 112 where thevessel V is not disposed between the light emitter 110 and the array112.

In fact, it is believed that particular regions of vessels, such asblood vessels, may undergo more pronounced pulsations that otherregions, which differences are reflected in differences in the pulsatilecomponent of the signal received from the array 112. More particularlyand with reference to blood vessels as a non-limiting example, as theheart pumps blood through the body, the muscular arteries pulse toaccommodate the volume of blood being directed through the body. As thisoccurs, the middle layer (or tunica media) of the vessel expands andcontracts. The expansion and contraction of the tunica media results ina relatively more significant change to the outer diameter of the vesselthan to the inner diameter of the vessel. It is believed that therelatively more significant change in outer diameter that occurs duringthe expansion and contraction of the vessel causes the greatestfluctuations in the AC signal (which, as mentioned above, is related tothe pulsations) over time at the edges of the vessel, as the outerdiameter oscillates between an expanded position A and a restingposition B (see FIG. 3).

Thus, according to the disclosed embodiments, the controller 114 iscoupled to the light sensor 112, and incudes a splitter 116 to separatethe first pulsatile component from the second non-pulsatile componentfor each element of the light sensor array 112. The controller 114 alsoincludes an analyzer 118 to quantify the size of the vessel V within theregion 102 proximate to the working end 104 of the surgical instrument106 based on the pulsatile component. To display, indicate or otherwiseconvey the size of the vessel V within the region 102, the controller114 may be coupled to an output device or indicator 130 (see FIG. 1),which may provide a visible, audible, tactile or other signal to theuser of the instrument 106.

In particular, the analyzer 118 may determine the magnitudes of thepulsatile components at the individual light sensors in the row of lightsensors. Further, the analyzer may determine a first peak magnitude anda second peak magnitude of the pulsatile components. The analyzer maymake the determination as to the first and second peak magnitudes afterfirst determining the locations of transitions in the pulsatile andnon-pulsatile components of the signal between higher and lowermagnitudes, as explained in detail below. In addition, the analyze 118may determine a resting outer diameter of the vessel V based on thefirst and second peak magnitudes of the pulsatile components.

According to certain embodiments, the analyzer 118 may determine theresting outer diameter of the vessel V by determining a first pair ofpositions along the row of light sensors where the magnitudes of thepulsatile component are a percentage (e.g., between 25% and 75%, such as50%) of the first (or second) peak magnitude, and a second pair ofpositions along the row of light sensors where the magnitudes of thepulsatile component are also the same percentage of the first (orsecond) peak magnitude, the second pair being disposed between the firstpair of positions along the row of light sensors. The analyzer thendetermines a first distance between the first pair of positions and asecond distance between the second pair of positions, and determines theresting outer diameter of the vessel as the average of the first andsecond distances. According to other embodiments, the analyzer 118 mayinstead use the inner pair of positions and a relationship between theinner and resting outer diameters. According to certain embodiments, thenon-pulsatile component may be used instead of the pulsatile component.

According to certain embodiments, the splitter 116 and the analyzer 118may be defined by one or more electrical circuit components. Accordingto other embodiments, one or more processors (or simply, the processor)may be programmed to perform the actions of the splitter 116 and theanalyzer 118. According to still further embodiments, the splitter 116and the analyzer 118 may be defined in part by electrical circuitcomponents and in part by a processor programmed to perform the actionsof the splitter 116 and the analyzer 118.

For example, the splitter 116 may include or be defined by the processorprogrammed to separate the first pulsatile component from the secondnon-pulsatile component. Further, the analyzer 118 may include or bedefined by the processor programmed to quantify the size of the vessel Vwithin the region 102 proximate to the working end 104 of the surgicalinstrument 106 based on the first pulsatile component. The instructionsby which the processor is programmed may be stored on a memoryassociated with the processor, which memory may include one or moretangible non-transitory computer readable memories, having computerexecutable instructions stored thereon, which when executed by theprocessor, may cause the one or more processors to carry out one or moreactions.

In addition to the system 100, the present disclosure includesembodiments of a method 200 of determining if a size of a vessel Vwithin a region 102 proximate to a working end 104 of a surgicalinstrument 106. The method 200 may be carried out, for example, using asystem 100 as described above in regard to FIG. 1. As illustrated inFIG. 4, the method 200 of operating the system 100 includes emittinglight at a working end of a surgical instrument at block 202 and sensinglight at the working end of the surgical instrument at an array of lightsensors comprising at least one row of light sensors at block 204. Asexplained above, the light emitted may include light of at least twodifferent wavelengths, and the sensing step may thus include sensinglight of at least two different wavelengths. As also noted above, threedifferent wavelengths of light may be used, and for example in thevisible range and the near-infrared range. According to one embodiment,the light used may have wavelengths of 660 nm, 810 nm, and 940 nm.

The method 200 continues at block 206 wherein a pulsatile component isseparated from a non-pulsatile component for individual sensors alongthe row of light sensors. The method 200 also includes determining themagnitudes of the pulsatile components at the individual light sensorsin the row of light sensors at block 208, determining a first peakmagnitude and second peak magnitude of the pulsatile components at block210, and determining a resting outer diameter of the vessel based on thefirst and second peak magnitudes of the pulsatile components at block212.

More particular, as illustrated in FIG. 5, the block 212 of the method200 of FIG. 4 may include one or more actions. In particular, asillustrated in FIG. 5, the action of block 212 may include determining afirst pair and a second pair of positions along the row of light sensorsat block 212-1, where the magnitudes of the pulsatile component of thefirst and second pair of positions are a percentage of the first (orsecond) peak magnitude. The second pair of positions is disposed betweenthe first pair of positions, as will be discussed relative to FIG. 6below. In addition, the action of block 212 may include determining afirst distance between the first pair of positions and a second distancebetween the second pair of positions at block 212-2, and determining theresting outer diameter of the vessel V as the average of the first andsecond distances at block 212-3.

To illustrate further the method 200 of operation of the system 100, asillustrated in FIGS. 4 and 5, a plot is provided in FIG. 6. Inparticular, FIG. 6 is a simulated plot of the magnitude of the pulsatile(AC) component for each element of a light sensor array and a plot ofthe magnitude of the non-pulsatile (DC) component for the same elementsof the array. The lines are marked AC and DC to differentiate the twoplots. According to this simulation, a vessel (specifically, a bloodvessel) is disposed between the light sensor array and a light emitterarray, with the vessel located generally between the light emitter arrayand the light sensor array in the region between 40 and 180 pixels.

As illustrated in FIG. 6, the DC signal plot decreases from a relativelyhigh value to a considerably lower value, and then increases from thelower value back to higher value at two different points (i.e., atpoints 300, 302) along the sensor array 112. In accordance with theobservations made above, the decrease in the magnitude of the DC signalin the region would be expected to occur where the vessel is disposedbetween the light emitter 110 and the light sensor 112, and it thereforemay be inferred that the vessel V is disposed between the point at whichthe DC signal plot transitions from the higher value to the lower value(i.e., point 300) and the point at which the DC signal plot transitionsfrom the lower value back to the higher value (i.e., point 302).

In addition, the AC signal increases significantly from a relatively lowvalue to a higher value at the point (i.e., point 304) on one side ofwhere the vessel is presumably located, and from a high value to a lowervalue (i.e., point 306) on the other side of where the vessel islocated. As also mentioned above, the relative increase in pulsatile(AC) signal is believed to occur where the vessel is disposed betweenthe light emitter 110 and the light sensor 112, and it therefore may beinferred that the vessel V is disposed between the point at which the ACsignal plot transitions from the lower value to the higher value (i.e.,point 304) and the point at which the AC signal plot transitions fromthe higher value back to the lower value (i.e., point 306).

While either the change in the DC signal or the change in the AC signalmay be used to define a region of interest (ROI), the combination of theinformation on the transitions in the AC signal may be combined with thetransitions in the DC signal to define an ROI to which the furtherconsideration of the pulsatile (AC) information is confined. That is,the system 100 (and more particularly the controller 120) may consider asubset of elements of all of the elements of the sensor array 112 inaccordance with this information. This may be particularly helpful ineliminating fluctuations unrelated to the vessel in individual sensorsalong the array. According to such embodiments, the transitions betweenhigher and lower values for each of the DC and AC plots are determined,and only the ROI where there is overlap between decreased DC magnitudeand increased AC magnitude is considered. As illustrated in FIG. 6, thisregion would be between the vertical bars (i.e., from about 40 pixels to180 pixels).

According to embodiments of the present disclosure, as illustrated inFIGS. 4 and 5, the resting diameter of the vessel may be calculatedbased on a correlation observed between the expanded outer diameter ofthe vessel and the inner diameter of the vessel. In particular, it hasbeen observed that the resting diameter of the vessel correlates to theaverage of the expanded outer diameter of the vessel and the innerdiameter of the vessel. To perform this calculation, the expanded outerdiameter (or line A) of the vessel is determined to be the distancebetween a first pair of points at which the AC magnitude isapproximately 50% of the peak AC magnitude: the leftmost occurrence(i.e., point 312) prior to (or leading) the leftmost AC peak magnitude(i.e., at point 308) and the rightmost occurrence (i.e., point 314)after (or lagging) the rightmost AC peak magnitude (i.e., at point 310).In addition, the inner diameter (or line C) is determined to be thedistance between a second pair of points at which the AC magnitude isapproximately 50% of the peak AC magnitude: the leftmost occurrence(i.e., point 316) after (or lagging) the leftmost AC peak magnitude(i.e., at point 308) and the rightmost occurrence (i.e., point 318)prior to (or leading) the rightmost AC peak magnitude (i.e., at point310). These distances may also be described as the distances between thetwo occurrences of 50% peak AC magnitude outside and inside the peak ACmagnitudes. It may also be said that the second pair is disposed betweenor inside the first pair.

It is not necessary to use the occurrences at 50% peak AC magnitudeaccording to all embodiments of the present disclosure. According toother embodiments, the inner diameter may be determined to be distancebetween the leftmost occurrence after (or lagging) the leftmost AC peakmagnitude and the rightmost occurrence prior to (or leading) therightmost AC peak magnitude of 5% peak AC magnitude, while the expandedouter diameter also was determined at the 5% peak AC magnitudeoccurrences described above.

Finally, as illustrated in FIG. 6, the resting outer diameter (line B)may be determined to be the average between the inner diameter (line C)and the expanded outer diameter (line A).

According to other embodiments of the present disclosure, thedetermination of the resting outer diameter of the vessel V may becalculated without reference to two pairs of positons along the row oflight sensors. More particular, the actions performed by the system 100at the block 212 of the method 200 of FIG. 4 to determine the restingouter diameter of the vessel V may be as illustrated in FIG. 7.According to this alternate method, the action of block 212 may includedetermining a pair of positions along the row of light sensors at block212-1′ in between the two positons where the peak magnitudes occur. Thesingle pair of positions (or “inner” pair) may occur where themagnitudes of the pulsatile component are a percentage of the first (orsecond) peak magnitude. For example, the inner pair may be defined bythe pair of positions between the positions where the peak magnitudesoccur corresponding to 50% of the first (or second) peak magnitude. Inaddition, the action of block 212 may include determining a distancebetween the inner pair at block 212-2′.

At block 212-3′, the distance between the inner pair of positions isthen used to calculate the resting outer diameter. According to thismethod, as was the case in the method of FIG. 5, the distance betweenthe inner pair of positons is representative of the inner diameter ofthe vessel V. Further, it believed that the inner diameter of a vesselundergoing expansion and contraction varies to a far lesser degree (ifat all) than the outer diameter. Moreover, it has been observed that thesignal from the edges of the vessel may be obscured by the presence oftissue disposed about the vessel. Consequently, rather than attemptingto approximate the outer diameter of the vessel, a relationship may bedetermined empirically between the inner diameter and resting outerdiameter, which relationship may be used to calculate the resting outerdiameter based on the measurement of the inner diameter, as determinedin accordance with the actions of blocks 212-1′ and 212-2′.

In its simplest form, the resting outer diameter may be determined to bea multiple of the inner diameter. According to other embodiments, theresting outer diameter may be calculated to be a multiple of the innerdiameter with the addition of a constant term. FIG. 8 is a graphcomparing the inner diameters and resting outer diameters of a set ofmuscular arteries. Based on this graph, a formula relating the outerdiameter (y) with the inner diameter (x) was determined (y=1.2x+0.9).Accordingly, for a given inner diameter determined at blocks 212-1′ and212-2′, the formula may be used to calculate the resting outer diameterat block 212-3′

A further embodiment of a method that may be practiced using, forexample, the system 100 illustrated in FIG. 1 is illustrated in FIG. 9.The method 220 illustrated in FIG. 9 addresses a complication that mayoccur if the vessel is grasped tightly between the jaws of aninstrument, such as is illustrated in FIGS. 1 and 2. In particular, thecompression of the vessel V between the jaws of the surgical instrument106 may change the pulsatile component of the signal, such that only asingle peak may be observed, instead of the two peaks as illustrated inFIG. 6.

The method 220 is similar to the method 200 in that light is emittedfrom the light emitter 110 at block 222, and the transmitted light issensed or detected by the light sensor array 112 at block 224. Thesystem 100 (or more particularly the controller 114) operates toseparate the non-pulsatile component of the signal from the pulsatilecomponent of the signal at block 226, and determines the magnitude ofthe pulsatile component at the individual sensors at block 228.

At block 230, the system 100 (controller 114) then makes a determinationas to the number of positons identified with a peak pulsatile magnitudeat block 230. According to certain embodiments, this determination maybe performed after a region of interest is identified using transitionsin the non-pulsatile component (e.g., from a higher magnitude to a lowermagnitude) and optionally in the pulsatile component (e.g., from a lowermagnitude to a higher magnitude). In fact, according to someembodiments, the determination at block 230 is performed once thetransition in the non-pulsatile component of the signal from a highermagnitude to a lower magnitude is identified.

If the determination is made at block 230 that two peaks are present,for example, then the method 220 may proceed to blocks 232, 234, 236,where a method similar to that described in regard to FIG. 7 isperformed (although it will be appreciated that a method similar to thatdescribed in regard to FIG. 5 may be substituted). If the determinationis made at block 230 that a single peak is present, then the method 220may proceed to blocks 242, 244, 246. In particular, a determination ismade at block 242 as to a single pair of positions along the row oflight sensors where the magnitudes of the pulsatile component are apercentage of the peak magnitude. For example, the pair may be definedby the pair of positions on either side of the peak magnitude (i.e., tothe left or the right of the position corresponding to the peakmagnitude) where the magnitude corresponds to 50% of the peak magnitude.In addition, the system 100 (controller 114) may determine the distancebetween this pair of positions at block 244. The system 100 may then usethe distance determined as the value for the inner diameter, andcalculate the resting outer diameter using the relationship establishedbetween inner diameter and outer diameter, in a process similar to thatdescribed in regard to block 212-3′ in FIG. 7.

It will be recognized that while the method 220 was described withreference to a determination as to how many peaks are present, thespecifics as to how this determination is performed may differ among thevarious embodiments. For example, the determination may be madeaccording to whether one peak is or two peaks are present.Alternatively, the determination may be made according to whether asingle peak is present, with subsequent actions taken dependent uponwhether the answer to this question is yes or no.

A further alternative to the methods described in FIGS. 4-9 is to usethe non-pulsatile component of the signal to determine the vessel outerdiameter. As illustrated in FIG. 10, the method 250 starts much like themethods 200, 220, in that light is emitted at block 252, transmittedlight is sensed or detected at block 254, and pulsatile andnon-pulsatile components are separated at block 256. Unlike the methodsabove, the system 100 (controller 114) interrogates the non-pulsatilecomponent at block 258 to determine the non-pulsatile magnitude atindividual sensors at block 258. Moreover, unlike the methods above, thesystem 100 determines the positions along the row of light sensors wherethe non-pulsatile magnitude transitions from a higher value to a lowervalue and where the non-pulsatile magnitude transitions from a lowervalue back to a higher value at block 260. This pair of positions, basedon these transitions in the non-pulsatile component of the signal, isthen used to determine the resting outer diameter at block 262. Forexample, the distance between the pair of positions may be used as theestimate for the resting outer diameter, or a relationship based onempirical data may be used to calculate the resting outer diameteraccording to the distance between the pair of positions where thenon-pulsatile component transitions.

According to certain embodiments, a system and method for determiningthe edge of a vessel may be provided in conjunction with the foregoing.It will be recognized, however, that the system and method of edgedetermination may also be used separately from the foregoing systems andmethods, although the system and method may utilize the same hardware interms of the light emitters 110, light sensors 112, and so on. Accordingto such embodiments, the controller 114 would include an analyzer 118 toquantify the edges of the vessel V within the region 102 proximate tothe working end 104 of the surgical instrument 106 based on the signalsreceived from the array 112. To display, indicate or otherwise conveythe edges of the vessel V within the region 102, the controller 114 maybe coupled to an output device or indicator 130 (see FIG. 1), which mayprovide a visible, audible, tactile or other signal to the user of theinstrument 106.

In particular, the analyzer 118 may determine the magnitudes of thepulsatile (AC) and non-pulsatile (DC) components at the individual lightsensors in the row of light sensors. In fact, the analyzer 118 may focuson the sensors at the distalmost edge of the instrument, i.e., the edgeclosest to the patient. Where the instrument 106 has a pair of jaws,this would be sensor(s) closest to the opening of the jaws. If thesensor senses a significant decrease in the DC magnitude and asignificant increase in the AC magnitude, the analyzer 118 may interpretthis event as signifying that the jaws, and more specifically thesensors at the distalmost edge of the jaws, have encountered something(tissue, blood vessel, etc.). Under the circumstances, the analyzer 118may use one of the afore-mentioned indicators 130 to alert the user.

It was recognized, however, that because the jaws of the surgicalinstrument 106 are in the open space in the beginning of the procedure,regardless of the type of material that is moved between the jaws, theanalyzer 118 will determine a decrease in the DC component magnitude anda corresponding increase in the AC component magnitude. As such, theuser may receive an alert, but would not know if the alert was becauseof the presence of a tissue, or of a vessel.

If, however, the analyzer 118 is determining the DC and AC magnitudesusing a recursive calculation, then there are new DC and AC magnitudescalculated with each incoming sample (data point). In such acircumstance, the analyzer 118 may be configured such that when theanalyzer 118 determines that a change has occurred in the DC and ACmagnitudes, the analyzer 118 collects data on a plurality of successiveAC magnitudes. If the jaws of the instrument 106 have tissue betweenthem, then light intensity absorbed may vary only to a small degree andthe magnitudes should not change much. Because the AC magnitude isproportional to the change in the observed values, it will alsoexperience a small increase in value with the following incomingsamples. If there is a blood vessel, or more particularly an edge of ablood vessel, at the distalmost edge of the jaws, then the magnitudeswill change in a sinusoidal fashion and the AC magnitudes should see adrastic change with the next incoming sample (data point).

In particular, the analyzer 118 may be configured to carry out an edgedetermination in keeping with the following relations or equations. Inthese relations or equations, the light intensity received by a sensorat the distalmost end of the jaw at time instant t is I(t). According tothe Beer's Law (Eqn. 1):I(t)=I ₀ e ^(−α(t)L)where α(t) (being a function of time) is the absorption coefficient ofthe material and L is the thickness of the material. The recursivevariance (the square of AC RMS) is computed using the following equation(Eqn. 2):

${v(t)} = {{\frac{t - 1}{t}{v\left( {t - 1} \right)}} + {\frac{1}{t}\left\lbrack {{I(t)} - {\overset{\_}{I}(t)}} \right\rbrack}^{2} + {\frac{t - 1}{t^{3}}\left\lbrack {{\overset{\_}{I}\left( {t - 1} \right)} - {I(t)}} \right\rbrack}^{2}}$where Ī(t) and Ī(t−1) denote the mean computed at time instants t andt−1, respectively. If the material is a tissue, α(t)=αwhich impliesI(t)≈I(t−1) which further signifies Ī(t)≈Ī(t−1). Evaluating theserelations results in the following (Eqn. 3):[Ī(t)−I(t)]≈[Ī(t−1)−I(t)]≈0

Combining Eqns. (2) and (3), results in the following (Eqn. 4):

${{v(t)} = \left. {\frac{t - 1}{t}{v\left( {t - 1} \right)}}\Rightarrow{{v(t)} \approx {{v\left( {t - 1} \right)}\mspace{11mu}{given}\mspace{14mu}{the}\mspace{14mu}{sampling}\mspace{14mu}{period}}} \right.},{{t - 1} \approx t}$In accordance with Eqn. 4, the variance or the AC RMS for tissue willalmost remain a constant over time. However, this will not be the casewhen a blood vessel is between the jaws (α(t)≠α). For a blood vessel,the signal would be sinusoidal and the variance/AC RMS will increasesharply before saturating at its actual value (around one time period).So looking at the values of v(t) 1≤t≤u where 2≤u T with T being the timeperiod of the signal or the heart rate.

This differentiating nature of these relations may further beaccentuated through the inclusion of a contrast enhancing factor. Inparticular, the DC magnitudes may be used as the contrast enhancingfactor. Specifically, it is believed that inspection of the changes inthe AC and DC magnitudes at the same time may add contrast between thetissue and the blood vessel. The larger the DC magnitude, the greaterthe probability of nothing (tissue or vessel) being present between thejaws. To implement the DC magnitude as a contrast enhancing factor,rather than making the edge determination based only on the change inthe AC magnitude, the analyzer 118 may make the edge determination basedon the ratio of AC/DC over time.

Thus, the analyzer 118 may be configured to determine the presence of anedge of a vessel according to the following method. First, the analyzer118 determines if there has been a significant change in the DC and theAC; if there has not been a significant change, then the analyzer 118determines that there nothing is present between the jaws or at thedistalmost end or edge of the surgical instrument 106. If the DC (Ī(0))and the AC (v(0)) values of the sensor at the end or edge of the jawschange, then the analyzer 118 determines that something (e.g., tissue,vessel) has been detected. The analyzer 118 then checks the ratio:

$r = {\frac{1}{u}{\sum\limits_{t = 1}^{u}\left\lbrack \frac{v(t)}{\overset{\_}{I}(t)} \right\rbrack}}$The ratio may then be compared to a threshold to differentiate betweentissue and a blood vessel.

This method also may be used to eliminate the tissue artifact. Based onthe ratio, the method may eliminate the DC decrease caused by the tissueand the corresponding AC peaks. This could improve a size (diameter)determination of the vessel and make size determination more robust.

Having thus described the surgical system 100, the method 200 and theprinciples of the system 100 and the method 200 in general terms,further details of the system 100 and its operation are provided.

Initially, while the emitter 110 and the sensor 112 are described asdisposed at the working end 104 of the surgical instrument 106, it willbe recognized that not all of the components that define the emitter 110and the sensor 112 need be disposed at the working end of the instrument106. That is, the emitter 110 may comprise a light emitting diode, andthat component may be disposed at the working end 104. Alternatively,the emitter 110 may include a length of optical fiber and a lightsource, the source disposed remotely from the working end 104 and thefiber having a first end optically coupled to the source and a secondend disposed at the working end 104 facing the sensor 112. According tothe present disclosure, such an emitter 110 would still be described asdisposed at the working end 104 because the light is emitted into thetissue at the working end 104 of the instrument 106. A similararrangement may be described for the sensor 112 wherein an optical fiberhas a first end disposed facing the emitter 110 (or perhaps moreparticularly, an end of the optical fiber that in part defines theemitter 110) and a second end optically coupled to other components thatcollectively define the sensor 112.

As also mentioned above, the light emitter 110 and light sensor 112 arepositioned opposite each other. This does not require the emitter 110and the sensor 112 to be directly facing each other, although this ispreferred. According to certain embodiments, the emitter 110 and sensor112 may be formed integrally (i.e., as one piece) with jaws 180 of asurgical instrument 106. See FIGS. 1 and 2. In this manner, lightemitted by the emitter 110 between the jaws 180 and through the tissueof interest may be captured by the light sensor 112.

The light emitter 110 may include one or more elements. According to anembodiment schematically illustrated in FIG. 2, the light sensor 112 mayinclude a first light emitter 110-1, a second light emitter 110-2, and athird light emitter 110-3. All of the light emitters may be adapted toemit light at a particular wavelength (e.g., 660 nm), or certainemitters may emit light at different wavelengths than other emitters.

As to those embodiments wherein the light emitter 110 is in the form ofan array including one or more light emitting diodes, as is illustratedin FIG. 2 for example, the diodes may be arranged in the form of aone-dimensional, two-dimensional or three-dimensional array. An exampleof a one-dimensional array may include disposing the diodes along a linein a single plane, while an example of a two-dimensional array mayinclude disposing the diodes in a plurality of rows and columns in asingle plane. Further example of a two-dimensional array may includedisposing the diodes along a line on or in a curved surface. Athree-dimensional array may include diodes disposed in more than oneplane, such as in a plurality of rows and columns on or in a curvedsurface.

The light sensor 112 according to the embodiments of the presentdisclosure also includes one or more individual elements. According toan embodiment illustrated in FIG. 2, the light sensor 112 may include afirst light sensor 112-1, a second light sensor 112-2, an n-th lightsensor 112-n, and so on. As was the case with the light emitters 110-1,110-2, 110-3, the light sensors 112-1, 112-2, 112-3 may be arranged inan array, and the discussion in regard to the arrays above applied withequal force here.

As discussed above, the system 100 may include hardware and software inaddition to the emitter 110, sensor 112, and controller 114. Forexample, where more than one emitter 110 is used, a drive controller maybe provided to control the switching of the individual emitter elements.In a similar fashion, a multiplexer may be provided where more than onesensor 112 is included, which multiplexer may be coupled to the sensors112 and to an amplifier. Further, the controller 114 may include filtersand analog-to-digital conversion as may be required.

As for the indicator 130 used in conjunction with controller 114, avariety of output devices may be used. As illustrated in FIG. 1, a lightemitting diode 130-1 may be attached to or incorporated into theassociated surgical instrument 106, and may even be disposed at theworking end 104 of the instrument 106. Alternatively or in addition, analert may be displayed on a video monitor 130-2 being used for thesurgery, or may cause an image on the monitor to change color or toflash, change size or otherwise change appearance. For example, FIG. 11illustrates a portion of a graphical user interface (GUI) that may bedisplayed on the video monitor 130-2, wherein a first region 132 isrepresentative of the location of a section of a vessel and surroundingtissue between the jaws of the surgical instrument 106 and a secondregion 134 is an enhanced representation of the section of vessel andsurrounding tissue illustrated in first region 132 with the vesselrepresented in a contrasting fashion to the surrounding tissue (e.g.,through the use of bands of different color for the vessel and thesurrounding tissue). The indicator 130 may also be in the form of orinclude a speaker 130-3 that provides an auditory alarm. The indicator130 also may be in the form of or may incorporate a safety lockout 130-4associated with the surgical instrument 106 that interrupts use of theinstrument 106. For example, the lockout could prevent ligation orcauterization where the surgical instrument 106 is a thermal ligaturedevice. As a still further example, the indicator 130 also may be in theform of a haptic feedback system, such as a vibrator 130-5, which may beattached to or formed integral with a handle or handpiece of thesurgical instrument 106 to provide a tactile indication or alarm.Various combinations of these particular forms of the indicator 130 mayalso be used.

As mentioned above, the surgical system 100 may also include thesurgical instrument 106 with the working end 104, to which the lightemitter 110 and light sensor 112 are attached (in the alternative,removably/reversibly or permanently/irreversibly). The light emitter 110and the light sensor 112 may instead be formed integrally (i.e., as onepiece) with the surgical instrument 106. It is further possible that thelight emitter and light sensor be attached to a separate instrument ortool that is used in conjunction with the surgical instrument or tool106.

As noted above, the surgical instrument 106 may be a thermal ligaturedevice in one embodiment. In another embodiment, the surgical instrument106 may simply be a grasper or grasping forceps having opposing jaws.According to still further embodiments, the surgical instrument may beother surgical instruments such as dissectors, surgical staplers, clipappliers, and robotic surgical systems, for example. According to stillother embodiments, the surgical instrument may have no other functionthan to carry the light emitters/light sensors and to place them withina surgical field. The illustration of a single embodiment is notintended to preclude the use of the system 100 with other surgicalinstruments or tools 106.

EXAMPLES

Experiments have been conducted using an embodiment of theabove-described system. The experiments and results are reported below.

The first set of experiments was conducted using an excised porcinecarotid artery. To simulate the pulsatile flow of fluid found in suchblood vessels, a submersible DC pump was used. The pump was capable ofoperation at between 40 and 80 cycles per minute, and could provide aflow rate that could be set to a particular value. The fluid used wasbovine whole blood to which heparin had been added and that wasmaintained at an elevated temperature to maintain physiologicalviscosity. For the experiments described below, the blood was pumped at60 cycles per minute and at a flow rate of 500 mL per minute.

A light emitter array was disposed opposite a light sensor array withthe excised porcine carotid artery disposed therebetween. The lightemitter array included five light emitting diodes that emitted light at660 nm. The light sensor array included a linear CCD array composed of250 elements arranged side-by-side, with each group or set of 20elements fitting into 1 mm of contiguous space along the array. Thesystem was operated for 10 seconds, with the results of the experimentsplotted in FIG. 12. The inner diameter of the vessel was determined byusing the distance between a pair of positions where the magnitude ofthe pulsatile component was 50% of the peak magnitude (i.e., line C inFIG. 12).

The second set of experiments was conducted using a light emitter arrayopposite a light sensor array, with the porcine carotid artery of aliving porcine subject disposed therebetween. The light sensor arrayincluded five light emitting diodes that emitted light at 660 nm. Thelight sensor array included 16 individual photodetector elements, eachelement being 0.9 mm wide. The elements were spaced with 0.1 mm betweenadjacent elements, such that each element occupied 1 mm of contiguousspace along the array. The system was operated for 15 seconds, with theresults of the experiment plotted in FIG. 13. The measurements for eachphotodetector were interpolated and converted to pixels to permit acomparison between the first set of experiments and the second set ofexperiments. Again, the inner diameter of the vessel was determined byusing the distance between a pair of positions where the magnitude ofthe pulsatile component was 50% of the peak magnitude (i.e., line C inFIG. 13).

In both sets of experiments, the inner diameters of the porcine arteriesdetermined using embodiments of the disclosed system were within amillimeter of the gross diameter measurements of the vessel. Forexample, relative to the first set of experiments, the inner diameterdetermined using the embodiment of the system was 4.7 mm, while thegross diameter measurement was 4.46 mm. As to the second set ofexperiments, the inner diameter determined using the embodiment of thesystem was 1.35 mm, and the gross diameter measurement was 1.1 mm.

For a third set of experiments, an embodiment of the system including anLED array emitting at 940 nm and a linear CCD array was used. The systemwas used to determine the resting outer diameters of four differentarteries (gastric, left renal, right renal, and abdominal) in a livingporcine subject. The system was operated for 10 seconds, and the innerdiameters were determined using a pair of points associated with 50% ofthe peak magnitude. After using the system to determine the innerdiameters, the arteries were excised and the gross vessel diameters wereobtained by quantifying the cross-section of the vessels at the point ofmeasurement along the vessels using NIH ImageJ software.

The results of the third group of experiments are illustrated in FIG.14. As indicated in the graph, there is a close correlation between theinner diameters determined using an embodiment of the system disclosedherein and the inner diameters measured using conventional techniques.The error bars represent the standard deviation of measurements of thesame artery taken at different points in time.

Additionally, four sets of experiments were conducted in regard to themethod of edge determination disclosed above. The experiments wereconducted using a u value of 4. Thus, for a sampling rate of FS, thetime taken to computer would be 4/FS which would be approximately 0.4 sfor the slowest sampling rate (10 Hz).

Experiment I

This experiment was conducted with a blood vessel at the edge of thejaw. As illustrated in FIGS. 15 and 16, the edge of the vessel isapparent based on the magnitude of the ratio.

Experiment II

This experiment was conducted with only tissue at the edge of the jaw.The magnitude of the ratio is higher at the edge but is not assignificant as that of the blood vessel (Experiment I). See FIGS. 17 and18.

Experiment III

This experiment was conducted with both a blood vessel and tissue insidethe jaws. As illustrated in FIGS. 19 and 20, there is a cleardistinction between the tissue and the blood vessel. Since the tissuewas moving with the vessel, the magnitude of the ratio for the tissue isnot very small. However, this does not present an issue as a large valuefor the ratio is present, resulting in the knowledge that the surgicalinstrument is reaching either a blood vessel or a tissue attached toone. In either event, the analyzer can provide an indication that thejaws are approaching blood vessel.

Experiment IV

This experiment was conducted using a blood vessel and an adipose tissuewith the tissue being at the end of the jaw. As illustrated in the FIGS.21 and 22, the ratio may be used to distinguish between the vessel andthe tissue.

In conclusion, although the preceding text sets forth a detaileddescription of different embodiments of the invention, it should beunderstood that the legal scope of the invention is defined by the wordsof the claims set forth at the end of this patent. The detaileddescription is to be construed as exemplary only and does not describeevery possible embodiment of the invention since describing everypossible embodiment would be impractical, if not impossible. Numerousalternative embodiments could be implemented, using either currenttechnology or technology developed after the filing date of this patent,which would still fall within the scope of the claims defining theinvention.

It should also be understood that, unless a term is expressly defined inthis patent using the sentence “As used herein, the term ‘______’ ishereby defined to mean . . . ” or a similar sentence, there is no intentto limit the meaning of that term, either expressly or by implication,beyond its plain or ordinary meaning, and such term should not beinterpreted to be limited in scope based on any statement made in anysection of this patent (other than the language of the claims). To theextent that any term recited in the claims at the end of this patent isreferred to in this patent in a manner consistent with a single meaning,that is done for sake of clarity only so as to not confuse the reader,and it is not intended that such claim term be limited, by implicationor otherwise, to that single meaning. Finally, unless a claim element isdefined by reciting the word “means” and a function without the recitalof any structure, it is not intended that the scope of any claim elementbe interpreted based on the application of 35 U.S.C. § 112(f).

What is claimed is:
 1. A surgical system, comprising: a surgicalinstrument having a working end; at least one light emitter disposed atthe working end of the surgical instrument; an array of light sensorsdisposed at the working end of the surgical instrument opposite the atleast one light emitter, the array of light sensors comprising at leastone row of light sensors, individual light sensors in the row of lightsensors adapted to generate a signal comprising a first pulsatilecomponent and a second non-pulsatile component; an output device; and anelectronic controller coupled to the array of light sensors and theoutput device, the controller comprising a splitter configured toseparate the first pulsatile component from the second non-pulsatilecomponent and an analyzer configured to determine the magnitudes of thepulsatile components at the individual light sensors in the row of lightsensors, to determine a first peak magnitude and a second peak magnitudeof the pulsatile components in the array of light sensors, the first andsecond peak magnitudes representing the greatest fluctuations in a wallof the vessel, to measure a distance between a first point along the rowassociated with the first peak magnitude and a second point along therow associated with the second peak magnitude, to determine a restingouter diameter of the vessel based on the distance between the first andsecond points associated with the first and second peak magnitudes ofthe pulsatile components, the analyzer configured to perform theforegoing with minimal delay such that the determination of the restingouter diameter may be characterized as real-time and to display orindicate the resting outer diameter to a user via the output device. 2.The surgical system according to claim 1, wherein the analyzerdetermines a pair of positions along the row of light sensors where themagnitudes of the pulsatile component are a percentage of the first orsecond peak magnitude, the pair of positions disposed between thepositions corresponding to the first and second peak magnitudes,determines a distance between the pair of positions, and determines theresting outer diameter of the vessel based on the distance.
 3. Thesurgical system according to claim 1, wherein the analyzer determines afirst pair and a second pair of positions along the row of light sensorswhere the magnitudes of the pulsatile component are a percentage of thefirst or second peak magnitude, the second pair of positions beingdisposed between the first pair of positions, determines a firstdistance between the first pair of positions and a second distancebetween the second pair of positions, and determines the resting outerdiameter of the vessel as the average of the first and second distances.4. The surgical system according to claim 3, wherein the percentage is50%.
 5. The surgical system according to claim 1, wherein the analyzeris configured to determine the magnitudes of the non-pulsatilecomponents, and the first and second peak magnitudes are disposed atpositions along the row of light sensors between a first transition ofthe non-pulsatile component from a higher magnitude to a lower magnitudeand a second transition of the non-pulsatile component from a lowermagnitude to a higher magnitude.
 6. The surgical system according toclaim 5, wherein the first and second peak magnitudes are also bothdisposed at positions along the row of light sensors between a firsttransition of the pulsatile component from a lower magnitude to a highermagnitude and a second transition of the pulsatile component from ahigher magnitude to a lower magnitude.
 7. The surgical system accordingto claim 1, wherein the first pulsatile component comprises analternating current signal component and the second non-pulsatilecomponent comprises a direct current signal component.
 8. The surgicalsystem according to claim 1, wherein the electronic controller comprisesa processor and memory, and the splitter comprises the processorprogrammed to separate the first pulsatile component from the secondnon-pulsatile component and the analyzer comprises the processorprogrammed to determine the magnitudes of the pulsatile components atthe individual light sensors in the row of light sensors, to determine afirst peak magnitude and a second peak magnitude of the pulsatilecomponents, to determine a resting outer diameter of the vessel based onthe first and second peak magnitudes along the row of light sensors. 9.The surgical system according to claim 8, wherein the analyzer comprisesthe processor programmed to determine a pair of positions along the rowof light sensors where the magnitudes of the pulsatile component are apercentage of the first or second peak magnitude, the pair of positionsdisposed between the positions corresponding to the first and secondpeak magnitudes, to determine a distance between the pair of positions,and to determine the resting outer diameter of the vessel based on thedistance.
 10. The surgical system according to claim 8, wherein theanalyzer comprises the processor programmed to determine a first pairand a second pair of positions along the row of light sensors where themagnitudes of the pulsatile component are a percentage of the first orsecond peak magnitude, the second pair of positions being disposedbetween the first pair of positions, to determine a first distancebetween the first pair of positions and a second distance between thesecond pair of positions, and to determine the resting outer diameter ofthe vessel as the average of the first and second distances.
 11. Thesurgical system according to claim 10, wherein the percentage is 50%.12. The surgical system according to claim 8, wherein the analyzer isconfigured to determine the magnitudes of the non-pulsatile components,and the first and second peak magnitudes are both disposed at positionsalong the row of light sensors between a first transition of thenon-pulsatile component from a higher magnitude to a lower magnitude anda second transition of the non-pulsatile component from a lowermagnitude to a higher magnitude.
 13. The surgical system according toclaim 12, wherein the first and second peak magnitudes are also bothdisposed at positions along the row of light sensors between a firsttransition of the pulsatile component from a lower magnitude to a highermagnitude and a second transition of the pulsatile component from ahigher magnitude to a lower magnitude.
 14. The surgical system accordingto claim 1, wherein the array of light sensors comprises a linear CCDarray.
 15. The surgical system according to claim 1, wherein thesurgical instrument comprises first and second opposing jaw elements,the at least one light emitter disposed on the first jaw element and thearray of light sensors is disposed on the second, opposing jaw element.16. The surgical system according to claim 15, wherein the surgicalinstrument is a grasper or a thermal ligature device.
 17. The surgicalsystem according to claim 1, wherein the output device comprises atleast one of light emitting diode, a video monitor, and a speaker. 18.The surgical system according to claim 17, wherein a graphical userinterface is displayed on the video monitor, the graphical userinterface comprising a first region representative of a location of thevessel.